On 26 August, Rev Al Sharpton, Martin Luther King III, and other civil rights activists will commemorate the 1963 march on Washington, which was organised to advocate for civil and economic rights for African Americans. This week, Jonathan Freedland sits down with Sharpton to discuss why he believes Martin Luther King Jr’s ‘I have a dream’ speech has been abused by some on the right, why he is still fighting for police reform, and how James Brown was so influential on his life